Assessment of the TROPOMI tropospheric NO2 product based on airborne APEX observations. - Tack, Frederik; Merlaud, Alexis; Iordache, Marian-Daniel; Pinardi, Gaia; Dimitropoulou, Ermioni; Eskes, Henk; Bomans, Bart; Veefkind, Pepijn; Van Roozendael, Michel (Atmospheric Measurement Techniques Discussions, 2020)